Multimedia:
HTML5 contains built in support for integrated multimedia files into web page via video and audio tags.

Multimedia:
The multimedia content was integrated in web pages via third party plugins such as Silverlight and flash.

HTML 5 has many new elements that are not present in HTML 4.

Added more elements to HTML 5 which does not exist in HTML 4.

HTML 5 has dropped certain elements.

The elements exist in HTML 4 has been removed from HTML 5 and few deprecated tags.

Is being developed by web hypertext application technology working group (WHATWG) and W3C HTML WG.

Was developed by World Wide Web consortium and WHATWG (web hypertext application technology working group).

User Geographical location:
On the other hand, in HTML5 is extremely easy to get the user location. HTML5’s JS GeoLocation can be leveraged to identify the location of the user accessing the website.

User Geographical location:
In HTML4, it was an extremely cumbersome task to get the geographical locations of the visitors visiting the site. It was even difficult when the website was accessed through mobile devices.

Client Side storage:
In HTML5, this issue has been addressed via Web SQL database and application cache that can be access via HTML5’s JavaScript interface.

Client Side storage:
In HTML4, in order to store important data on client side, browser’s cache was used. However, that cache is limited and doesn’t support relational storage mechanism.

JavaScript Threading Mechanism:
In HTML4, JavaScript and the browser interface with which user interacts, run in the same thread which affects performance.

Browser Compatibility:
On the other hand, HTML5 is still in the process of evolution and the currently available tags are being modified and also new tags are being added. Therefore, HTML5 lags behind HTML4 in terms of compatibility with the browsers.

Browser Compatibility:
HTML4 is an established standard for developing browser applications and has been in use for more than 10 years. For this reason, HTML4 is compatible with almost all web-browsers.